Kirby Morgan 525 317 Helmet Spares Kit For SL 17A B Neck Ring Assembly 4 position 58633 4 position The wavy pattern cut from the top of the blade (created by a fireman from Sweden) and along the inside of the handle let you place a piece of rope (between the half open blade and handle) and scissor the blade shut especially convenient for cutting rope in and around flesh without having to fully open expose the knife's blade Kirby Morgan 525 317 Helmet Spares Kit For SL 17A B PART NUMBER DESCRIPTION QTY 510 008 O ring 2 510 010 O ring 1 510 211 O ring 1 510 260 O ring 1 510 446 O ring 1 510 481 O ring 1 510 521 Head Cushion 1 510 533 Neck Dam 1 510 550 Oral Nasal Valve 1 510 561 Valve